How does this category work, do I actually have to get every single block? Like Leaves, Pistons, Glowstone, etc. Or do I have to collect every block from the "Building Blocks" Category

You have to obtain every obtainable block. However I will add a no nether if you want.

Items are not needed

how many blocks are there

i need help /info for the run

Me too

You can find out by going into creative mode in the project and looking at building blocks section when you are done.

only place able blocks only right

It is not place it is obtain every obtainable block

Redstone, Piston and TNT, Crafting Table, Furnace, etc too?

Mushroom, sign and that type of items are not necessary?

Things that do not count as blocks ex: mushrooms, signs, redstone items, and unobtainable things such as ores and leaves.